# python3

class Parent(object):
    x = 1


class Child1(Parent):
    pass


class Child2(Parent):
    pass


print(Parent.x, Child1.x, Child2.x)

Child1.x = 2

print(Parent.x, Child1.x, Child2.x)

Parent.x = 3

print(Parent.x, Child1.x, Child2.x)